1. Field of the Invention
The present invention relates to an engine valve driving apparatus, and more particularly to an engine valve driving apparatus including a valve driving cam which is controlled to move radially by a hydraulic system according to engine operating conditions.
2. Description of the Prior Art
In the field of internal combustion engines, engine valve driving apparatus including an engine valve controlled to work in cooperation with a valve driving cam according to engine operating conditions are well known. One such engine valve driving apparatus is described in Japanese Patent Unexamined Publication No. 58-133,409 laid open Aug. 9, 1983. This engine valve driving apparatus has a valve driving cam which is fixed to a camshaft in the rotational directions and can be moved in the radial direction by a hydraulic system according to engine speed. However, the device taught by the above-mentioned Japanese Patent Unexamined Publication No. 58-133,409 is structurally unfavorable in stability in the high engine speed region of operation. That is, the valve driving cam in the high engine speed region is merely protruding from the camshaft without any stopper mechanism, and for that reason is inherently unstable.